First off, there's thing called humor. Perhaps you haven't heard of it, perhaps you don't see it here. There's also this thing called context. Earlier comments were talking about cold water. "Cold" varies from region to region. In my area it comes out at about 4° C. I have no problem washing my ass and am not a baboon. Nor am I inclined toward name-calling. I just prefer to use something closer to skin temperature than it is to ice.

It senses spicy, because spicy isn't actually a form of taste, but rather just your pain sensors being triggered by a chemical, like for example capsaicin (chilis) or piperine (black pepper).

Wikipedia says for capsaicin:

By binding to TRPV1 receptors, capsaicin produces similar sensations to those of excessive heat or abrasive damage, such as warming, tingling, itching, or stinging, explaining why capsaicin is described as an irritant on the skin and eyes or by ingestion.

So, I guess, the butthole would in a sense be good at feeling temperature, but only for excessive/painful heat.

But also, people generally report that this problem largely goes away when they start using a bidet.
So far, the explanation that makes the most sense to me, is that you get micro-scratches from the toilet paper, and then the capsaicin etc. will really be able to irritate the broken skin.